The Pathology Core has been developed in conjunction with the clinical and basic sciences projects. The procurement of tissue, analysis of samples and staging of the excised specimens has been in operation for several years and is conducted within the Division of Surgical Pathology. The goal of this core is to assure a complete diagnostic evaluation of surgical specimens. Paraffin blocks and snap frozen normal and tumor tissues of rectal adenocarcinomas and recurrent colon cancers will be used for these purposes. Gross and microscopic examination of mouse gastrointestinal tumors will also be performed. In addition to pathological examination, the Pathology Core will perform immunohistochemical analysis of tumor samples with primary antibody stains that include proliferation and prognostic markers (Ki-67, p53, Topoisomerase II, p27 and p21/WAF1/CIP1, Bcl-2 and Fhit) and markers of mismatch repair deficiencies (hMSH2, hMLH1 and Hmsh6). The presence and distribution of the PLA2G2A (secretory non-pancreatic phospholipase 2) will be investigated in normal human colonic mucosa and in colorectal tumors. Immunohistochemical stains will be interpreted in conjunction with the results form the basic research projects (Projects 2 and 3) and the Molecular Genetics Core. The Pathology Core will handle and distribute all tissues, prepare DNA (and RNA if sufficient tissue is available) from microdissected tumor/normal samples, and document/report its finding for correlation of marker expression with patient's response to therapy and outcome.